U.S. import prices rose marginally in May as the cost of petroleum rebounded, but the trend continued to point to subdued imported inflation pressures.

The Labor Department said on Thursday import prices edged up 0.1 percent last month after falling 0.5 percent in April.

Economists polled by Reuters had forecast import prices rising 0.2 percent. In the 12 months through May, prices increased 0.4 percent, advancing for the first time since July.

A sluggish global economy and slack in the domestic labor market is keeping inflation pressures muted, giving the Federal Reserve room to keep its ultra-easy monetary policy for a while.

The U.S. central bank slashed overnight interest rates to a record low of zero to 0.25 percent in December 2008 and is not expected to start raising them before the second half of 2015.

Last month, imported food prices fell 0.8 percent after declining by the same margin in April. Imported petroleum prices increased 1.1 percent after falling 1.2 percent in April.

Import prices excluding petroleum fell for a second straight month. The Labor Department report also showed export prices ticked up 0.1 percent in May after falling 1.0 percent the prior month. In the 12 months through May, export prices increased 0.5 percent, the largest gain since June last year.